Final answer:
The energy consumed by a 2500 watt electric heater over 3 hours is 7.5 kWh. The cost of this energy is Nu 15, calculated by multiplying 7.5 kWh by the cost per kWh of Nu 2.
Step-by-step explanation:
The question involves calculating the energy consumed by an electric heater and the cost of that energy consumption. Given that an electric heater has a power rating of 2500 watts and it's used for 3 hours, the energy consumed can be calculated using the formula for electrical energy (E = Pt), where P is the power in kilowatts and t is the time in hours. In this case, the heater uses 2.5 kilowatts (since 2500 watts is equivalent to 2.5 kilowatts) for 3 hours, thus consuming 7.5 kilowatt-hours (kWh).
The cost of this energy consumption can be determined by multiplying the total kWh by the cost per kWh, which is Nu 2 in this scenario. Therefore, the energy cost for using the heater for 3 hours is Nu 15 (7.5 kWh × Nu 2 per kWh).